The present invention relates generally to desalination of seawater and, more particularly, to methods and an apparatus for desalination of seawater using reverse osmosis membranes.
The desire to make drinkable, potable water out of seawater has existed for a long time. Several approaches can be taken to remove the salt and other chemicals. Water distillation is one way to approach the goal, but may not be commercially feasible. In this approach, water is heated to separate the solids from the liquid and therefore remove the salt solids. Another approach is electrodialysis in which the ions forming the salt are pulled by electric forces from the saline water through membranes and thereafter concentrated in separate compartments. This approach is also very expensive. A third approach to desalination is through reverse osmosis. This method uses pressure to force salty feed water against membranes which allows the relatively salt free water to pass through, but not much of the salts or other minerals. But due to the high production and capital costs, desalination systems are not widely used for making large scale supplies of public drinking water.
Efforts have been made to increase the efficiency of reverse osmosis systems in general and specifically, with respect to a desalination system, to lower operating and fixed costs. Some efforts have been directed at the improving the efficiency of the filtration systems, other efforts have been directed at the design and application of filter membranes, multi stage filtering and nano-filtration methods. Other efforts have also been directed at improving the efficiency of other aspects of a reverse osmosis system. For example, some efforts have been directed at the membrane filtration system replacement method by monitoring the silt density and at the application of particular feed water pressures.
Each of these efforts may increase the efficiency of the desalination system, but these efforts may not sufficiently reduce the cost of the system for use for public ware supply. What is needed is a desalination system that processes seawater into potable water more cost effectively for use for public water supply.